Black infrared-transmitting coating material, preparation method and application thereof

Abstract

The present application relates to the field of paint technology, and discloses a black infrared transmission paint, a preparation method and application thereof. The black infrared transmission paint comprises a resin composition (including silicone-modified acrylic resin and polyester resin), a black pigment filler composition (including yellow pigment, blue pigment, red pigment, filler particles and solvent) and isocyanate curing agent; the silicone-modified acrylic resin is formed by hydrolysis and condensation reaction of trimethoxysilane (with self-closed isocyanate group) and vinyltriethoxysilane under catalyst and water to form an organic silicon material containing olefin and silicon hydroxyl, and then cross-linking reaction of the organic silicon material and acrylic resin under a free radical initiator. The paint can better wrap and fix the pigment, and has high infrared light transmission rate; the coating has good heat resistance stability and aging migration resistance; the obtained infrared reflective photovoltaic back plate has high infrared light reflectivity and long-term stability, and can ensure long-term stable growth of module power.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a black infrared-transmitting coating, its preparation method, and its application. Background Technology

[0002] Solar photovoltaic (PV) modules, as an environmentally friendly and clean energy source, have been widely promoted in recent years. PV modules installed on industrial and commercial building rooftops often have aesthetic and light pollution prevention requirements, therefore black PV modules are commonly used.

[0003] Typically, for a 60-cell photovoltaic (PV) module, the spacing between the cells is generally 2mm-4mm. Therefore, the area not covered by the cells accounts for more than 2% of the total PV module area. This means that more than 2% of sunlight passes through the gaps between the cells and does not reach the cell surface for absorption and utilization. Furthermore, black PV modules made with conventional black backsheets have strong absorption across the entire spectrum of light. The absorption of most infrared wavelengths by these backsheets is directly converted into heat, causing the PV module to heat up. For every 1°C increase in temperature, the PV module's power generation efficiency decreases by approximately 0.4%. Therefore, the 2% of sunlight that passes through the gaps between the cells in a black PV module but is not utilized is easily absorbed by the conventional black backsheet and converted into heat, further reducing the module's power generation efficiency.

[0004] Therefore, if this 2% of sunlight can be fully utilized, it will help improve the power generation efficiency of photovoltaic modules. Thus, existing technologies, such as CN115926545A, can combine a weather-resistant black coating with infrared transmission properties with a substrate that has infrared reflection capabilities to obtain a photovoltaic backsheet with infrared light reflection capabilities. This not only reduces the operating temperature of the photovoltaic module but also enhances the absorption and utilization of reflected light by the cells, thereby improving the power generation efficiency of the photovoltaic module.

[0005] However, the existing photovoltaic backsheet (CN115926545A) with infrared light reflection function still needs improvement in the transmittance of the weather-resistant black coating in the infrared light band (750nm-1100nm). Moreover, the weather-resistant black coating has poor encapsulation and fixation of the three-color pigments. During long-term use in complex and harsh outdoor environments, the weather-resistant black coating has poor heat resistance stability and aging migration resistance. Therefore, the existing photovoltaic backsheet has low infrared reflectivity and poor long-term stability of infrared reflectivity, which is not conducive to maintaining the long-term stable growth of photovoltaic module power. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a black infrared-transmitting coating, its preparation method, and its application.

[0007] Based on this, the present invention discloses a black infrared-transmitting coating comprising the following components in parts by weight: 40-70 parts of resin composition, 15-40 parts of black pigment and filler composition, and 2-15 parts of isocyanate curing agent.

[0008] The resin composition is a mixture of 20-40 parts of silicone-modified acrylic resin and 20-40 parts of polyester resin.

[0009] Organosilicon-modified acrylic resin is formed by hydrolysis and condensation of 10-20 parts of blocked isocyanate groups trimethoxysilane and 10-20 parts of vinyltriethoxysilane in the presence of 0.1-2 parts of catalyst (such as acetic acid or hydrochloric acid) and 5-10 parts of water to form an organosilicon material containing olefins and silanol groups. Then, it is cross-linked with 50-80 parts of acrylic resin in the presence of 0.1-5 parts of free radical initiator (such as azobisisobutyronitrile).

[0010] Preferably, the acrylic resin is a low molecular weight acrylic resin with a molecular weight of 3000-5000.

[0011] The closed isocyanate group of trimethoxysilane has a self-closed isocyanate group.

[0012] Preferably, the blocked isocyanate group trimethoxysilane is formed by the isocyanate group propyltrimethoxysilane and 3,5-dimethylpyrazole through the isocyanate group blocking reaction; the blocked isocyanate group trimethoxysilane can only release the isocyanate group again when heated to above 120°C for self-polymerization reaction.

[0013] The synthesis principle of organosilicon-modified acrylic resin is as follows:

[0014] 1. The blocking reaction principle of isocyanate groups is as follows:

[0015]

[0016] 2. The principle of the hydrolysis reaction is as follows: the closed isocyanate groups of trimethoxysilane and vinyltriethoxysilane are hydrolyzed into the corresponding silanols.

[0017]

[0018] 3. The principle of condensation reaction is as follows: silanol is condensed into organosilicon materials containing olefins and silanols.

[0019]

[0020] 4. The principle of cross-linking reaction is as follows: Organosilicon materials containing olefins and silanol groups react with acrylic resin through a cross-linking reaction to form organosilicon-modified acrylic resin.

[0021]

[0022] The black pigment and filler composition includes 3-20 parts of yellow pigment, 25-40 parts of blue pigment, 35-60 parts of red pigment, 15-25 parts of filler particles, and 70-90 parts of solvent (such as ethyl acetate or butyl acetate).

[0023] Preferably, the brightness and chromaticity values ​​of the pigment and filler composition are 20≤L*≤24, 0.8≤a*≤0.1 and -0.8≤b*≤0.2.

[0024] The yellow pigment is at least one of BASF L1100, BASF L1600, BASF 2060, Pigment Yellow 119, Pigment Yellow 184, Pigment Yellow 139, Pigment Yellow 138, Pigment Yellow 191, Pigment Yellow 185, Bayer Iron Yellow 3910, Bayer Iron Yellow 4910, Bayer Iron Yellow 420, benzidine yellow, benzimidazole, and perylene-phenanthrene type yellow pigments; the yellow pigment is preferably BASF L1600, Pigment Yellow 185, or Pigment Yellow 139.

[0025] The blue pigment is at least one of Pigment Blue 15, Pigment Blue 67, Pigment Blue 70, Pigment Blue 136, anthraquinone-type blue pigment, and phthalocyanine-type blue pigment; the preferred blue pigment is Pigment Blue 15.

[0026] The red pigment is at least one of BASF L2817, Bayer 4140, Bayer 4130, Bayer 4180, Bayer 4110, Pigment Red 177, Pigment Red 108, Pigment Red 119, Pigment Red 132, Pigment Red 179, Pigment Red 242, Pigment Red 254, Pigment Red 265, Pigment Red 269, and Pigment Red 291; the preferred red pigment is Pigment Red 177 or Pigment Red 179.

[0027] Preferably, the filler particles are core-shell structured silica-coated materials (such as octadecenol-coated silica), wherein the core of the silica-coated material is silica and the outer layer is an organic material. The organic material is at least one of fatty alcohols, silane coupling agents, and monomer polymers. The fatty alcohol is at least one of nonanol, n-decanol, cetyl alcohol, oleyl alcohol, and octadecenol; the silane coupling agent is at least one of vinyltriethoxysilane and propenyltrimethoxysilane; and the monomer polymer is at least one of polystyrene, polyvinyl chloride, polycaprolactam, and polyethylene. The organic material is preferably a fatty alcohol, more preferably octadecenol, cetyl alcohol, or oleyl alcohol.

[0028] This invention also discloses a method for preparing a black infrared-transmitting coating, comprising the following preparation steps:

[0029] Step S1: Synthesis of silicone-modified acrylic resin:

[0030] Step S11: Add 3-isocyanate group propyltrimethoxysilane and 3,5-dimethylpyrazole in a molar ratio of 1:1-1.2, stir and mix, and react at 55-65℃ for 25-35 minutes to obtain blocked isocyanate group trimethoxysilane.

[0031] Step S12: Mix 50-80 parts of acrylic resin, 10-20 parts of blocked isocyanate group trimethoxysilane, 10-20 parts of vinyltriethoxysilane and 0.1-2 parts of catalyst evenly, then heat to 60-70℃, slowly add 5-10 parts of water dropwise, and continue the reflux reaction for at least 1 hour after the addition is complete, then heat to 105-115℃, add 0.1-5 parts of free radical initiator dropwise, and continue the reaction for at least 2 hours to obtain organosilicon modified acrylic resin.

[0032] Step S2: Mix 20-40 parts of polyester resin and 20-40 parts of silicone-modified acrylic resin from step S12 until homogeneous to obtain a resin composition.

[0033] Step S3: Add 3-20 parts (preferably 4-15 parts) of yellow pigment, 25-40 parts (preferably 30-35 parts) of blue pigment, 35-60 parts (preferably 40-50 parts) of red pigment, and 15-25 parts of filler particles to 70-90 parts of solvent, grind evenly, filter, and obtain a black pigment and filler composition.

[0034] Step S4: Mix 40-70 parts of the resin composition from step S2, 15-40 parts of the pigment and filler composition from step S3, and 2-15 parts of the isocyanate curing agent. After thorough mixing, filter to obtain a black infrared-transmitting coating.

[0035] Preferably, step S11 is as follows: 3-isocyanate group propyltrimethoxysilane and 3,5-dimethylpyrazole are added in a molar ratio of 1:1, stirred and mixed, and reacted at 60°C for 30 minutes to obtain blocked isocyanate group trimethoxysilane.

[0036] Preferably, step S12 is as follows: 60 parts of acrylic resin, 15 parts of blocked isocyanate group trimethoxysilane, 10 parts of vinyltriethoxysilane and 0.2 parts of acetic acid are mixed evenly, then the temperature is raised to 65°C, 8 parts of water are slowly added dropwise over 30 minutes, after the addition is complete, the reaction is continued under reflux for 1 hour, then the temperature is raised to 110°C, 2 parts of azobisisobutyronitrile are added dropwise, and the reaction is continued for 2 hours to obtain organosilicon modified acrylic resin.

[0037] Preferably, step S2 is: mixing 30 parts of polyester resin and 30 parts of silicone-modified acrylic resin evenly to obtain a resin composition.

[0038] Preferably, step S3 is as follows: 4 parts of yellow BASF L1600, 35 parts of Pigment Blue 15, 45 parts of Pigment Red 177, 20 parts of octadecenol-coated silica, and 1 part of dispersant BYK356 (a dispersant is required when adding inorganic pigments) are added to 80 parts of ethyl acetate, ground evenly, and filtered to obtain a black pigment and filler composition. The brightness and chromaticity values ​​(L*, a*, b*) of this pigment and filler composition are 20 ≤ L* ≤ 24, 0.8 ≤ a* ≤ 0.1, and -0.8 ≤ b* ≤ 0.2.

[0039] Preferably, step S4 is as follows: 60 parts of the resin composition from step S2, 30 parts of the pigment and filler composition from step S3, and 10 parts of the isocyanate curing agent are mixed, stirred thoroughly and mixed evenly, and then filtered to obtain a black infrared-transmitting coating.

[0040] This invention also discloses an application of a black infrared-transmitting coating, which is used to prepare an infrared-reflective photovoltaic backsheet. The application process is as follows:

[0041] A black infrared-transmitting coating is applied to the side of a white substrate near the solar cell and cured to form a black infrared-transmitting coating on the surface of the white substrate.

[0042] Preferably, the white substrate includes a photovoltaic substrate and a weather-resistant coating on the side of the photovoltaic substrate away from the solar cells; wherein the photovoltaic substrate and / or the weather-resistant coating is a white reflective layer.

[0043] Preferably, the photovoltaic substrate is a semi-transparent or ultra-white polyester film with a thickness of 275-325 μm (e.g., 290 μm or 300 μm); the weather-resistant coating is a white or black weather-resistant coating with a thickness of 6-20 μm, preferably 8-10 μm. Specifically, the photovoltaic substrate is white, and the weather-resistant coating is either white or black; or, the photovoltaic substrate is a semi-transparent photovoltaic substrate, and the weather-resistant coating is white.

[0044] Preferably, the thickness of the black infrared-transmitting coating is 6-20 μm, and more preferably 6 μm.

[0045] The black infrared-transmitting coating of the present invention has an average transmittance of less than 5% in the wavelength range of 400-750nm, while its average transmittance is greater than 87% in the infrared wavelength range of 750-1100nm.

[0046] The present invention also discloses a photovoltaic module, which includes a photovoltaic front panel, a front encapsulation film, a battery cell, a rear encapsulation film and a photovoltaic back panel stacked from top to bottom, wherein the photovoltaic back panel is an infrared reflective photovoltaic back panel as described above in the present invention.

[0047] In the black infrared-transmitting coating of the present invention, the closed isocyanate groups trimethoxysilane and vinyltriethoxysilane, after hydrolysis and condensation, crosslink with low molecular weight acrylic resin to form a unique low molecular weight organosilicon-modified acrylic resin. This resin has good adhesion to photovoltaic substrates and can firmly fix the pigment molecules in the black infrared-transmitting coating within the black infrared-transmitting coating. After curing, it has a glass-like appearance and exhibits significant glass properties, such as a hard coating, scratch resistance, heat resistance, cold resistance, solvent resistance, and water resistance.

[0048] This silicone-modified acrylic resin has a large number of functional groups (such as hydroxyl groups and self-closed isocyanate groups). During coating curing, it can cross-link with isocyanate curing agents. Moreover, its self-closed isocyanate groups can automatically release NCO upon heating, realizing intermolecular self-polymerization reaction, increasing the cross-linked network structure between coating molecules, better encapsulating and fixing pigments, and preventing color migration. Therefore, this silicone-modified acrylic resin, combined with polyester resin, black pigment and filler composition and isocyanate curing agent, makes the black infrared-transmitting coating more weather-resistant, heat-resistant, stable, and resistant to aging and migration.

[0049] Furthermore, low molecular weight silicone-modified acrylic resins exhibit lower curing reactivity, making them more readily involved in the curing reaction at lower temperatures (150°C). During curing, they more easily and quickly capture and fix pigments. Moreover, these low molecular weight silicone-modified acrylic resins possess superior reactivity, crosslinking properties, and film-forming properties, enabling complete crosslinking and curing of the coating in a short time. Consequently, no components migrate into the product, preventing migration contamination.

[0050] Furthermore, conventional color migration often involves moisture, causing pigments to diffuse from the coating into the encapsulating film of the photovoltaic backsheet, resulting in a lighter coating color due to the hydrophobic nature of silicone. However, the silicone-modified acrylic resin of this invention exhibits excellent hydrophobicity, delaying the contact between pigments and moisture, thus preventing pigment migration. Moreover, the silicone-modified acrylic resin has no unsaturated bonds in its molecular structure, making it difficult for ultraviolet light to break down or crosslink it. After the pigment is fixed by the silicone-modified acrylic resin, its black infrared light transmits through the coating, showing no loss of gloss, discoloration, or powdering over a long period, demonstrating outstanding weather resistance.

[0051] Furthermore, the filler particles in the black infrared-transmitting coating are core-shell structured silica-coated materials, with a silica core and an organic outer layer. This allows the filler particles to not only facilitate uniform mixing and dispersion with the three pigments (yellow, blue, and red), but also improve the compatibility of the pigment-filler composition with the resin composition. This enables the resin composition to better coat and fix the three pigments, thus enhancing the heat resistance (i.e., after 180℃ and 2h dry heat treatment, the infrared reflective photovoltaic backsheet shows no significant color deviation, ensuring high reflectivity over a long period) and aging migration resistance (after UV+DH and 120kWh composite aging treatment, the infrared reflective photovoltaic backsheet shows minimal yellowing and the black infrared-transmitting coating does not shed powder or peel off).

[0052] Compared with the prior art, the present invention has at least the following beneficial effects:

[0053] In the black infrared-transmitting coating of the present invention, the organosilicon-modified acrylic resin has a large number of various functional groups (such as hydroxyl groups and self-closed isocyanate groups). When heated, it can release NCO, which can rapidly increase the cross-linked network structure between coating molecules, better encapsulate and fix the pigment, and prevent color migration. The organosilicon-modified acrylic resin, combined with polyester resin, black pigment and filler composition and isocyanate curing agent, makes the black infrared-transmitting coating more weather-resistant, heat-resistant, stable, and resistant to aging and migration.

[0054] Moreover, this black infrared-transmitting coating absorbs almost all visible light (400-750nm), resulting in a visually black photovoltaic backsheet that ensures the aesthetic appeal of the photovoltaic module's front. Furthermore, this black infrared-transmitting coating has high transmittance in the infrared band (750nm-1100nm). When applied to a white substrate (such as a white photovoltaic substrate or a white weather-resistant coating), the infrared light passing through the coating is strongly reflected back to the solar cells, improving the cells' absorption and utilization of sunlight, thus increasing module power. The reflected infrared light is also reused by the solar cells (rather than being absorbed by the photovoltaic backsheet and converted into heat), improving the cooling effect of the photovoltaic backsheet.

[0055] Therefore, this invention coats a black infrared-transmitting coating onto a white substrate to produce an infrared-reflective photovoltaic backsheet. This effectively solves the defects of conventional black photovoltaic backsheets, such as low light reflectivity, light absorption converted into heat energy causing photovoltaic module heating, and color migration of black pigment after lamination. The resulting infrared-reflective photovoltaic backsheet exhibits excellent resistance to color migration, ensuring the aesthetic appeal of the black module's front while possessing excellent infrared reflection performance and improving the cooling effect of the photovoltaic backsheet. The infrared-reflective photovoltaic backsheet has high reflectivity (especially in the 750-1200nm wavelength band) and good long-term reflectivity stability, ensuring long-term power growth of the photovoltaic module using the infrared-reflective photovoltaic backsheet and effectively improving the power generation efficiency and output of the photovoltaic module using the infrared-reflective photovoltaic backsheet. Attached Figure Description

[0056] Figure 1 The infrared spectrum of propyltrimethoxysilane with 3-isocyanate group before reaction in step S11 of Example 1.

[0057] Figure 2 The infrared spectrum of the blocked isocyanate group trimethoxysilane after the reaction in step S11 of Example 1.

[0058] Figure 3 The infrared spectra of the acrylic resin before and after the reaction in step S12 of Example 1 are shown.

[0059] Figure 4 This is a graph showing the transmittance data of the black infrared-transmitting coating obtained in Example 1.

[0060] Figure 5 This is a schematic diagram of the infrared reflective photovoltaic backsheet obtained in Example 1.

[0061] The reference numerals are as follows: 1. Black infrared-transmitting coating; 2. Photovoltaic substrate; 3. White weather-resistant coating. Detailed Implementation

[0062] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0063] Example 1

[0064] The preparation method of a black infrared-transmitting coating according to this embodiment includes the following preparation steps:

[0065] Step S1: Synthesis of silicone-modified acrylic resin:

[0066] Step S11: Add 3-isocyanate group propyltrimethoxysilane and 3,5-dimethylpyrazole in a molar ratio of 1:1, stir and mix, and react at 60°C for 30 minutes to obtain blocked isocyanate group trimethoxysilane.

[0067] Step S12: Mix 60 parts of acrylic resin, 15 parts of the blocked isocyanate group trimethoxysilane from step S11, 10 parts of vinyltriethoxysilane, and 0.2 parts of acetic acid evenly. Then heat to 65°C and slowly add 8 parts of water dropwise over 30 minutes. After the addition is complete, continue the reflux reaction for 1 hour. Then heat to 110°C and add 2 parts of azobisisobutyronitrile. Continue the reaction for 2 hours to obtain organosilicon modified acrylic resin.

[0068] Step S2: Mix 30 parts of polyester resin and 30 parts of silicone-modified acrylic resin from step S12 until homogeneous to obtain a resin composition.

[0069] Step S3: Add yellow pigment, blue pigment and red pigment to an organic solvent in a weight ratio of 3-20:25-40:35-60. Continue to add filler particles and dispersant to the organic solvent, grind with a ball mill for 2 hours, filter with gauze, and obtain a black pigment and filler composition.

[0070] In practice, the yellow, blue, and red pigments need to be fine-tuned to make the pigment and filler composition black, and the brightness and chromaticity values ​​(L*, a*, b*) of the pigment and filler composition are 20≤L*≤24, 0.8≤a*≤0.1, and -0.8≤b*≤0.2.

[0071] Specifically, the yellow, blue, and red pigments are selected from BASF L1600 (yellow), Pigment Blue 15, and Pigment Red 177, respectively, with 4 parts of yellow pigment, 35 parts of blue pigment, and 45 parts of red pigment; the organic solvent is 80 parts of ethyl acetate; the filler particles are 20 parts, which are octadecenol-coated silica; and the dispersant is 1 part of BYK356.

[0072] Step S4: Mix the resin composition from step S2, the pigment and filler composition from step S3, and the curing agent in parts by weight of 40-70:15-40:2-15 (specifically 60:30:10). After thorough mixing, filter the mixture through gauze to obtain a black infrared-transmitting coating of this embodiment.

[0073] Specifically, the curing agent is an isocyanate curing agent (such as Bayer N3390 or a blocked isocyanate curing agent). If the curing agent is a blocked isocyanate curing agent, an organotin catalyst (such as dibutyltin dilaurate) accounting for 0.4% of the total weight of the black infrared transmitting coating needs to be added.

[0074] This embodiment describes the application of a black infrared-transmitting coating. The black infrared-transmitting coating prepared in this embodiment is applied to the preparation of an infrared-reflective photovoltaic backsheet. The specific application process is as follows:

[0075] A roller coating method is used, employing a roll-to-roll processing technique to apply a black infrared-transmitting coating to the side of the photovoltaic substrate 2 (e.g., a semi-transparent photovoltaic substrate with a thickness of 290 μm) closest to the solar cell (i.e., the inner surface of the photovoltaic substrate 2). The other side of the photovoltaic substrate 2, away from the solar cell (i.e., the outer surface of the photovoltaic substrate 2), is coated with a white weather-resistant coating. The coating is then cured in segmented drying tunnels at 100℃, 140℃, 160℃, and 190℃ for 2 minutes each, at a curing linear speed of 90 meters per minute, thus obtaining an infrared-reflective photovoltaic backsheet (the structure of the infrared-reflective photovoltaic backsheet is as follows). Figure 5 (As shown).

[0076] Specifically, see Figure 5 The thickness of the black infrared-transmitting coating 1 formed after the black infrared-transmitting coating of the infrared reflective photovoltaic backsheet is controlled at 6-20μm (e.g., 6μm, 10μm, 15μm or 20μm). In this embodiment, the black infrared-transmitting coating 1 is preferably 6μm; the thickness of the white weather-resistant coating 3 is 8-10μm (e.g. 9μm).

[0077] Example 2

[0078] The black infrared-transmitting coating, its preparation method, and its application in this embodiment are all based on Example 1, except that:

[0079] In this implementation, the thickness of the black infrared-transmitting coating of the infrared reflective photovoltaic backsheet after curing is 20μm.

[0080] Comparative Example 1

[0081] This comparative example of a black infrared-transmitting coating, its preparation method, and its application are all based on Example 1, except that:

[0082] In step S3 of Example 1, all the yellow, blue, and red pigments were replaced with carbon black as pigments, while the total weight percentage of the pigments remained unchanged.

[0083] Comparative Example 2

[0084] This comparative example of a black infrared-transmitting coating, its preparation method, and its application are all based on Example 1, except that:

[0085] In Example 1, step S3, all the yellow, blue, and red pigments were replaced with conventional perylene black pigments (such as copper chrome black) while keeping the total weight percentage of the pigments unchanged.

[0086] Comparative Example 3

[0087] This comparative example of a black infrared-transmitting coating, its preparation method, and its application are all based on Example 1, except that:

[0088] The synthesis step of the organosilicon-modified acrylic resin in step S1 of Example 1 is omitted, and the 30 parts of organosilicon-modified acrylic resin in step S2 of Example 1 are replaced with 30 parts of acrylic resin.

[0089] Comparative Example 4

[0090] This comparative example of a black infrared-transmitting coating, its preparation method, and its application are all based on Example 1, except that:

[0091] The synthesis step of the silicone-modified acrylic resin in step S1 of Example 1 is omitted, and the 30 parts of silicone-modified acrylic resin in step S2 of Example 1 are replaced with 30 parts of a mixture of conventional silicone resin and acrylic resin, wherein the weight ratio of silicone resin to acrylic resin is 1:2.

[0092] Comparative Example 5

[0093] This comparative example of a black infrared-transmitting coating, its preparation method, and its application are all based on Example 1, except that:

[0094] The synthesis step of the silicone-modified acrylic resin in step S1 of Example 1 is omitted, and the 30 parts of silicone-modified acrylic resin in step S2 of Example 1 are replaced with 30 parts of commercially available silicone-modified acrylic resin (such as RB-237 resin).

[0095] Performance testing

[0096] 1. Infrared spectroscopy was performed on the 3-isocyanate group propyltrimethoxysilane before the reaction and the blocked isocyanate group trimethoxysilane after the reaction in step S11 of Example 1. The infrared spectra obtained were as follows: Figure 1 and Figure 2 .

[0097] See Figure 1 The NCO absorption peak before the reaction is at 2263 cm⁻¹. -1 See also: Figure 2 The absorption peak disappeared after the reaction. This indicates that the NCO group of the blocked isocyanate group in the trimethoxysilane was effectively blocked after the reaction.

[0098] 2. Infrared spectroscopy was performed on the acrylic resin before and after the reaction in step S12 of Example 1. The infrared spectra obtained are as follows: Figure 3 As shown ( Figure 3 In the image, gray represents the infrared spectrum of the acrylic resin before the reaction in step S12 of Example 1; black represents the infrared spectrum of the acrylic resin after the reaction in step S12 of Example 1.

[0099] See Figure 3 Compared to the acrylic resin before the reaction, the infrared spectrum of the acrylic resin after the reaction is in the range of 1000-1200 cm⁻¹. -1 An absorption peak of Si-O-Si appeared at 3376 cm⁻¹. -1 Numerous OH absorption peaks (specifically Si-OH absorption peaks) were observed. Therefore, the organosilicon-modified acrylic resin was obtained after the reaction in step S12 of Example 1.

[0100] 3. The transmittance of the black infrared-transmitting coating (coated on a quartz plate) prepared in Example 1 was tested. The coating thickness was 10 μm. The transmittance data is shown in the figure below. Figure 4 As shown.

[0101] See Figure 4 The black infrared-transmitting coating prepared in Example 1 has an average transmittance of 4.8% in the 400-750nm visible light band, which can promote the full absorption of the solar cell in the 400-750nm visible light band; while the black infrared-transmitting coating prepared in Example 1 has an average transmittance of 87.9% in the 750-1200nm infrared light band.

[0102] 4. The performance of the infrared reflective photovoltaic backsheets prepared in Examples 1-2 and Comparative Examples 1-5 and the power of their photovoltaic modules were tested respectively. The test results are shown in Table 1 below. In Table 1, MEK refers to the resistance to methyl ethyl ketone (MEK) wiping test.

[0103] Table 1

[0104]

[0105] As can be seen from Table 1:

[0106] (1) In Examples 1-2, when the black infrared-transmitting coating is thicker, the reflectivity of the infrared-reflective photovoltaic backsheet (especially the reflectivity in the 750-1200nm band) will decrease, and the power of its photovoltaic module will also decrease. After being subjected to dry heat treatment at 180℃ for 2 hours, the infrared-reflective photovoltaic backsheets of Examples 1-2 did not show a large deviation in colorimetric values, and can ensure high reflectivity for a long time. Moreover, after being subjected to a composite aging treatment of UV+DH and 120kwh, the infrared-reflective photovoltaic backsheets of Examples 1-2 showed little yellowing and the black infrared-transmitting coating did not shed powder. Therefore, the infrared-reflective photovoltaic backsheets of Examples 1-2 have high reflectivity (especially the reflectivity in the 750-1200nm band) and good long-term reflectivity stability, which can ensure the long-term power growth of its photovoltaic module.

[0107] (2) Compared with Example 1, the black infrared-transmitting coating in the infrared reflective photovoltaic backsheet of Comparative Example 1 uses carbon black as a pigment, so the reflectivity of the infrared reflective photovoltaic backsheet of Comparative Example 1 (especially the reflectivity in the 750-1200nm band) is extremely low, and its photovoltaic module power is also low. In contrast, the black infrared-transmitting coating in the infrared reflective photovoltaic backsheet of Example 1 is made by mixing yellow, blue and red pigments to achieve black, so the photovoltaic module power made using the infrared reflective photovoltaic backsheet of Example 1 is increased by 2.2% compared with Comparative Example 1.

[0108] (3) Compared with Example 1, the black infrared transmission coating in the infrared reflective photovoltaic back panel of Comparative Example 2 uses copper chromium black pigment as pigment. Therefore, after the infrared reflective photovoltaic back panel of Comparative Example 2 is subjected to dry heat treatment at 180°C for 2 hours, a large color deviation or color migration occurs, and the reflectivity will further decrease during use. Moreover, after the infrared reflective photovoltaic back panel of Comparative Example 2 is subjected to UV+DH and 120kwh composite aging treatment, it yellows significantly, which further reduces the power of its photovoltaic module.

[0109] (4) Compared with Example 1, the black infrared transmitting coating in the infrared reflective photovoltaic backsheets of Comparative Examples 3-5 used acrylic resin, a mixture of conventional silicone resin and acrylic resin, and commercially available existing silicone-modified acrylic resin (such as RB-237 resin) to replace the black infrared transmitting coating in Example 1. Therefore, after UV+DH and 120kwh composite aging treatment, the infrared reflective photovoltaic backsheets of Comparative Examples 3-5 showed significant yellowing, risk of color migration, severe powder shedding, and easy peeling of the black infrared transmitting coating, making it difficult to ensure the high reflectivity of their infrared reflective photovoltaic backsheets in the long term, and thus difficult to ensure the power growth of their photovoltaic modules in the long term.

[0110] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present invention.

[0111] The technical solution provided by the present invention has been described in detail above. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A black infrared-transmitting coating, characterized in that, It comprises the following components in parts by weight: 40-70 parts of resin composition, 15-40 parts of black pigment and filler composition, and 2-15 parts of isocyanate curing agent; The resin composition is a mixture of 20-40 parts of silicone-modified acrylic resin and 20-40 parts of polyester resin. The organosilicon-modified acrylic resin is formed by hydrolysis and condensation of 10-20 parts of blocked isocyanate-group trimethoxysilane and 10-20 parts of vinyltriethoxysilane in the presence of 0.1-2 parts of catalyst and 5-10 parts of water to form an organosilicon material containing olefins and silanol groups, and then crosslinking it with 50-80 parts of acrylic resin in the presence of 0.1-5 parts of free radical initiator. The closed isocyanate group trimethoxysilane has a self-closed isocyanate group; the closed isocyanate group trimethoxysilane can release the isocyanate group again when heated to above 120°C. The pigment and filler composition comprises 3-20 parts of yellow pigment, 25-40 parts of blue pigment, 35-60 parts of red pigment, 15-25 parts of filler microparticles, and 70-90 parts of solvent.

2. The black infrared-transmitting coating according to claim 1, characterized in that, The blocked isocyanate group trimethoxysilane is formed by the blocking reaction of 3-isocyanate group propyltrimethoxysilane and 3,5-dimethylpyrazole via the isocyanate group blocking reaction.

3. The black infrared-transmitting coating according to claim 1, characterized in that, The acrylic resin is a low molecular weight acrylic resin with a molecular weight of 3000-5000; the catalyst is acetic acid or hydrochloric acid.

4. The black infrared-transmitting coating according to claim 1, characterized in that, The filler particles are core-shell structured silica-coated materials, with a core of silica and an outer layer of organic material. The organic material is at least one of fatty alcohols and silane coupling agents.

5. A method for preparing a black infrared-transmitting coating according to any one of claims 1-4, characterized in that, The preparation steps include the following: Step S1: Synthesis of silicone-modified acrylic resin: Step S11: Add 3-isocyanate group propyltrimethoxysilane and 3,5-dimethylpyrazole in a molar ratio of 1:1-1.2, stir and mix, and react at 55-65°C for 25-35 minutes to obtain blocked isocyanate group trimethoxysilane. Step S12: Mix 50-80 parts of acrylic resin, 10-20 parts of blocked isocyanate group trimethoxysilane, 10-20 parts of vinyltriethoxysilane and 0.1-2 parts of catalyst evenly, then heat to 60-70°C, slowly add 5-10 parts of water dropwise, and continue to reflux for at least 1 hour after the addition is complete, then heat to 105-115°C, add 0.1-5 parts of free radical initiator dropwise, and continue to react for at least 2 hours to obtain organosilicon modified acrylic resin; Step S2: Mix the formulated amount of polyester resin and silicone-modified acrylic resin evenly to obtain a resin composition; Step S3: Add the prescribed amounts of yellow pigment, blue pigment, red pigment, and filler particles to the solvent, grind them evenly, filter, and obtain a black pigment and filler composition; Step S4: Mix the formulated amount of resin composition, pigment and filler composition and isocyanate curing agent, stir thoroughly and mix evenly, then filter to obtain black infrared transmitting coating.

6. The method for preparing a black infrared-transmitting coating according to claim 5, characterized in that, Step S11 is as follows: 3-isocyanate group propyltrimethoxysilane and 3,5-dimethylpyrazole are added in a molar ratio of 1:1, stirred and mixed, and reacted at 60°C for 30 minutes to obtain blocked isocyanate group trimethoxysilane.

7. The method for preparing a black infrared-transmitting coating according to claim 5, characterized in that, Step S12 is as follows: 60 parts of acrylic resin, 15 parts of blocked isocyanate group trimethoxysilane, 10 parts of vinyltriethoxysilane and 0.2 parts of acetic acid are mixed evenly, then the temperature is raised to 65°C, and 8 parts of water are slowly added dropwise over 30 minutes. After the addition is complete, the reaction is refluxed for 1 hour, then the temperature is raised to 110°C, and 2 parts of azobisisobutyronitrile are added dropwise. The reaction is continued for 2 hours to obtain organosilicon modified acrylic resin.

8. The application of a black infrared-transmitting coating according to any one of claims 1-4, characterized in that, The application process of using black infrared-transmitting coating to prepare infrared-reflective photovoltaic backsheets is as follows: A black infrared-transmitting coating is applied to the side of a white substrate near the solar cell and cured to form a black infrared-transmitting coating on the surface of the white substrate.

9. The application of a black infrared-transmitting coating according to claim 8, characterized in that, The white substrate includes a photovoltaic substrate and a weather-resistant coating located on the side of the photovoltaic substrate away from the solar cells; wherein the photovoltaic substrate and / or the weather-resistant coating are white reflective layers; The photovoltaic substrate is a semi-transparent or ultra-white polyester film with a thickness of 275-325μm; the weather-resistant coating is a white or black weather-resistant coating with a thickness of 8-10μm. The thickness of the black infrared-transmitting coating is 6-20 μm.

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